(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of removing unwanted nickel or cobalt in the fabrication of integrated circuits.
(2) Description of the Prior Art
In the fabrication of integrated circuits, metal silicides are often formed through a rapid thermal annealing (RTA) process. Metals such as titanium, cobalt, and nickel are typically used in salicidation. After RTA, the unreacted metal is typically removed by wet chemicals. For example, SC-1 (Standard Clean-1 comprising ammonium hydroxide, hydrogen peroxide, and de-ionized water) may be used to remove titanium, SC-2 (Standard Clean-2 comprising hydrochloric acid, hydrogen peroxide, and de-ionized water) and a mixture of sulfuric acid, hydrogen peroxide, and water (SPM) may be used to remove cobalt and nickel. Nitric acid and SPM are also used for the stripping (rework) of cobalt and nickel on bare silicon wafers. The drawbacks of using wet chemicals include the expensiveness of high purity chemicals, disposal costs, and the corrosive nature of the chemicals.
U.S. Pat. No. 4,659,426 to Fuller et al teaches using a carbonyl source for etching a metal, metal silicide, or polysilicon. U.S. Pat. No. 5,358,601 to Cathey shows the etching of a polycide using CO.sub.2 and a halogen-containing gas. U.S. Pat. No. 5,259,923 to Hori et al etches the polysilicon layer of a polycide using carbon monoxide. U.S. Pat. No. 5,091,050 to Fujino et al etches aluminum and a transition metal using carbon monoxide.